Fluoropyrimidines

ABSTRACT

A process of the preparation of fluoro substituted pyrimidines useful as lubricants, dyestuffs, pharamaceutical agents and pesticides which includes the isolated monofluoro-trichloro- and difluoro-dichloropyrimidines by reacting polyhalopyrimidines with hydrofluoric acid under increased temperature and pressure.

United rates Patent 1 3,694,444 Klauke et al. 51' Sept. 26, 1972 [54] FLUOROPYRHMIDHNES [56] References Cited [72] Inventors: Erich Klauke, Odenthal-Hahnen-' FOREIGN PATENTS OR APPLICATIONS berg; Hans-Samuel Bien, Burscheid, both f Germany 1,440,673 4/1966 France [73] Assignee: Farbeniabriken Bayer Aktien- OTHER PUBLICATIONS gesellschafi Leverkusen Germany CA. 65, 3869 (1966) Protsenko et al. [22] Filed: Nov. 1,1967

Primary Examiner-Alex Mazel [21] Appl. No.: 679,652 Assistant Examiner-R. V. Rush Atrorn'ey-Plumley, Tyner and Sandt [30] Foreign Application Priority Data [57] ABSTRACT A process of the preparation of fluoro substituted Dec. 16, Germany ..F pyrimidines useful as lubricants, dy ff pharamaceutical agents and pesticides which includes the isolated monofluoro-trichloroand difluoro- 52/51, 260/ dichloropyrimidines by reacting polyhalopyrimidines [51] Int. Cl. ..C07d 51/36 with hydrofluoric acid under increased temperature and pressure.

Field of Search ..260/251 1 Claim, No Drawings 1 FLUOROPYRIMIDINES The production of fluorinated pyrimidines by exchanging the chlorine atoms in tetrachloropyrimidine for fluorine is known. in the literature, silver fluoride (Am. Soc. 82, 4115 [1960]) and alkali metal fluorides (Belgian Pat. Specification No. 660,907) are described as fluorinating agents.

Whereas the use of silver fluoride is not taken into consideration for industrial processes for reasons of costs, the use of, for example, potassium fluoride, as described in the Belgian Patent Specification, is a technically interesting and feasible process. Consequently, a fairly large number of publications have discussed the use' of alkali fluorides as fluorinating agents for aromatic compounds, such as hexachlorobenzene and pentachloropyridine,. by the exchange of chlorine for fluorine.

A survey of these reactions can be found, inter alia, in A. K. Barbour, P. Thomas, Ind.eng.Chem. 58 {1966],48-55.

Thefluorination of cyanuric chloride, i.e. of an acid chloride, with, inter alia, anhydrous hydrofluoric acid,

is described in German Pat.

Specification No.

I 1,044,091. In the specialexample of execution, SbCl, is used as catalyst for this fluorination. The fact that this instruction explicitly uses a catalyst indicates that, even in the fluorination of an acid chloride in which the C1 to be exchanged is substantially more reactive, compared with the genuinely aromatically linked chlorine substituent, a reaction with hydrofluoric acid alone, i.e. without a catalyst, was not possible or not thought to be possible.

Surprisingly, it has now been found that in polyhalopyrimidines in which at least one of the halogen substituentsin the 2-, 4- and/or 6-position is a chlorine or bromine substituent, as in 2,4,5,6- tetrachloroor -bromo-pyrimidine and 2,4,6-trichloroor -bromopyrimidine, chlorine or bromine substituents in the 2-, 4- and/or 6-position can be exchanged for fluorine atoms by the action of anhydrous hydrofluoric acid under comparatively gentle conditions and with high yields. v

t The process according to the invention is characterized in that polyhalopyrimidines in which at least one of the halogen substituents in the 2-, 4- and/or 6- position is a chlorine .or' bromine substituent,v are reacted with anhydrous hydrofluoric acid at temperatures of 80 to 180 C and under increased pressure with the exchange of at least one chlorine or bromine substituent in the 2-, 4- and/or 6-position for a fluorine substituent.

As polyhalopyrimidines containing a chlorine or bromine substituent in the 2, 4- and/or 6-position, 2,4,5,6-tetrachloropyrimidine and 2,4,6- trichloropyrimidine can primarily be used. The corresponding bromine derivatives are also usable. Furthermore it is possible to isolate the monofluorotrichloro and difluoro-dichloro or -bromo-pyrimidine compounds which are intermediarily formed in the reaction of tetrachloroor tetrabromopyrimidine according to the invention and are, in part, known from other literature references, and to use them as starting compounds for another reaction with fluorohydric acid according to the invention.

The ranges of temperature preferred for the reaction according to the invention are 120 to 160 C and those of the pressure are to 50 atm. excess pressure.

The reaction according to the invention can be carried out by first placing the polyhalopyrimidine, for example, tetrachloropyrimidine or trichloropyrimidine, into an autoclave of high quality steel fitted with stirrer, adding the anhydrous hydrofluoric acid and applying a slight protective pressure of an inert gas, such as nitrogen. The autoclave is then heated to the desired temperature. The gaseous hydrogen halide formed in the course of the reaction can escape via a release valve, possibly together with any excess protective gas, during or after the heating. The pressure is generally released at 35 to 45 atm. excess pressure. When the reaction is completed, the autoclave is cooled and released, and the content is worked up by distillation.

The product of the, process is a monoor polyfluoropyrimidine which may contain chlorine or bromine substituents. The number of fluorine substituents introduced depends on the duration of the reaction and the temperature applied. Fluoropyrimidines which still contain exchangeable chlorine or bromine substituents, can either be used as such for further reactions or they can be used as starting materials to another fluorination according to the process of the invention. It is possible, for example, to obtain difluoro-dichloropyrimidine and a trifluoromonochloro-pyrimidin'e from monofluorotrichloropyrimidine, and a trifluoromonochloropyrimidine from difluorodichloropyrimidine. Chlorine or bromine substituents in the Sposition of the pyrimidine ring are exchanged for a fluorine substituent only with difficulty, or not at all, due to their known reaction inertia.

Products which can be obtained by the present process are, for example, monofluorotrichloropyrimidine and, if tetrachloropyrimidine is used, presumably 4- fluoro-2,5,6-trichloropyrimidine, difluoro-dichloropyrimidine, presumably 2,4-difluoro- 5,6-dichloropyrimidine, and 2,4,6-trifluoro-5- chloropyrimidine. In general, mixtures of monoand polyfluorinated pyrimidines are formed under the conditions of the process. However, it is always possible to produce one of the compounds as main component by a suitable selection of the reaction conditions. Reaction conditions affecting the composition of the products are, besides the temperature and the time, also the molar ratio of the starting components and the intensity with which the reaction mixture is mixed. The higher the molar ratio of anhydrous hydrofluoric acid to polyhalopyrimidine, the higher is the degree of fluorination which can be achieved under otherwise identical conditions. In general, a molar ratio HF to polyhalopyrimidine of 6 to 12 1 is preferred. it may sometimes be of advantage to go beyond or to remain below this molar ratio since, for example, a high excess of hydrofluoric acid reduces the solubility of the resultant hydrohalic acid, especially of hydrogen chloride, in the reaction mixture and thus favors the removal thereof from the reaction space. On the other hand, a lower molar ratio is advantageous for the preparation of the low stage of fluorination.

The products of the process are valuable preliminary products for the preparation of dyestuffs by condensing, for instance, 2 mols of amino group-containing dyestuffs with 1 mol of a difluoropyrimidine thus connecting the amino groups of the two dyestuff molecules via a pyrimidine bridge member. The

EXAMPLE 1 A nickel autoclave of 0.5 liters capacity fitted with reflux condenser and stirrer is charged with 140 g tetrachloropyrimidine and 100 ml of anhydrous hydrofluoric acid, and a nitrogen pressure of 12 atm. excess pressure is applied. The autocalve is then heated to 130 C while stirring, and the reaction mixture is kept at this temperature for hours. By means of a control valve arranged behind the reflux condenser, the pressure in the apparatus is kept between 22 and 25 atm. excess pressure by occasional release. Nitrogen and HG] escape during the release. After 10 hours, the autoclave is cooled to room temperature, the remaining pressure is released and the bulk of the unconsumed hydrofluoric acid is removed by applying a slight vacuum. The residue is distilled in a distillation apparatus of high quality steel. There are obtained 104 g of crude distillate of n 1.5170 and 1 1 g of residue from distillation containing practically unchanged starting material. According to gas-chromatographic analysis, the crude distillate is composed as follows: 6.3 percent trifluoro-monochloropyrimidine, 38.8 percent difluoro-dichloropyrimidine, 46.8 percent monofluorotrichloropyrimidine and 6.6 percent of unchanged tetrachloropyrimidine.

The components can be isolated therefrom by distillation; they have the following physical properties and yield the following values in the elementary analysis: monofluoro-trichloropyrimidine: b.p. 195C u 1 .5392 presumably 4-fluoro-2,5,6-trich1oropyrimidine according to gas chromatography:

90.5% monofluoro-trichloro-pyrimidine 9.5% difluoro-dichloro-pyrimidine calculated C 23.85 Cl 52.90 F 9.43 N 13.90 found 23.72 51.90 101013.64 difluoro-dichloropyrimidine: b.p. 156 C n 1.4908 presumably 2,4-difluoro-5,6-dichloropyrimidine calculated C 25.93 Cl 38.40 F 20.53 N 15.15 found 26.21 37.65 20.70 15.15 2,4,6trifluoro-S-chloropyrimidine: b.p.l 16C m, 1.4390

the following Table shows the influence of the various variable conditions on the composition of the reaction mixture:

Mix- Temp. time molar n 3F/ 2F/ lF/ 4C1 ture C hrs. ratio 1C1 2C1 3C1 HF/Py crude dist.

A 10 8 1.5170 6.3 38.8 46.8 6.6 B 130 10 8 1.5008 13.5 43.1 34.9 2.5 C 10 8 1.4645 48.6 37.7 7.05 0.2 D 150 3 16 1.4495 71.8 19.9 2.00

A slow stir-ring B intense shaking C, D rapid stirrer Py tetrachloropyrimidine EXAMPLE 2 In an apparatus as described in Example 1, 100 g of a monofluoro-trichloropyrimidine obtained according to Example 1 and 80 m1 HF are reacted at C for 2 hours, while keeping the resultant l-lCl pressure at between 45 and 40 atm. excess pressure by occasional release. The mixture is worked up by distillation. There are obtained 77 g of a reaction product of n 1.5052 which according to the gas chromatogram has the following composition.

1 1 percent trifluoro-chloropyrimidine 49.5 percent difluoro-dichloropyrimidine 33.5 percent unchanged starting material.

EXAMPLE 3 In an autoclave as described in Example 1, 140 g of a difluoro-dichloropyrimidine obtained according to Example 1 and 90 m1 HF are fluorinated at 160 C to C for 2 hours. After distillation, there are obtained 124 g of a reaction product of n 1.4692, which according to the gas chromatogram contains 46.7 percent trifluoro-chloropyrimidine.

EXAMPLE 4 We claim: 1. A process for the preparation of fluoro-substituted pyrimidines which comprises reacting polyhalopyrimidines in which at least one of the halogen substituents in the 2-, 4- and/or 6-position is a chlorine or bromine substituent, with anhydrous hydrofluoric acid at a temperature of from about 80 C to about 180 C under increased pressure with the exchange of at least-one chlorine or bromine substituent in the 2-, 4- and/or 6-position for a fluorine substituent. 

